Thermoplastic polymers, e.g., polyamides, polyesters, polyphenylene sulfide, polyoxymethylene, polyolefins, styrene polymers, and polycarbonates, are characterized as polymers that exhibit exceptional mechanical and electrical properties, as well as good moldability and chemical resistance. However, these polymers may exhibit inadequate tribological properties when utilized in some friction environments, e.g., plastic to metal, and plastic to plastic interfaces. While many lubricating compositions have been applied to thermoplastic polymers to improve friction and wear properties of shaped articles prepared therefrom, some applications prohibited the use of certain lubricants because of possible contamination, e.g., food handling, clothing preparation and volatile environments.
Attempts have been made to improve the friction properties and reduce the surface wear of articles prepared from thermoplastic polymers by incorporating lubricants directly into the polymer matrix prior to the fabrication of shaped articles therefrom. Many materials, including solid lubricants and fibers (e.g., graphite, mica, silica, talc, boron nitride and molybdenum sulfide), paraffin waxes, petroleum and synthetic lubricating oils, and other polymers (e.g., polyethylene and polytetrafluoroethylene) have been added to thermoplastic polymers to improve friction and wear properties. However, the addition of many of these additives in various combinations to thermoplastic polymers, while improving tribological properties have reduced other desirable physical and mechanical properties. Some additives have proven satisfactory for short terms at low speeds and loads. However, friction characteristics of many of these lubricants significantly deteriorate over long periods of time under increased loads.
There is a desire for a non-toxic, self-lubricating thermoplastic compositions possessing surface wear resistance and low friction properties under increasing loads over long periods of time. A suitable composition, when fabricated into a shaped article, should maintain the desired mechanical and physical properties long associated with thermoplastic polymers, and be safely utilized in food handling and clothing manufacturing industries.